Parcel not delivered...

and may not be delivered before Monday...which is, of course, much too late.
Why does it take more than a week for a small parcel to travel from one capital city to another within Downunder? 
I posted a parcel last Saturday. It was done over the counter at  our local post office. I know the staff in there and they are helpful. They will have done the right thing. 
I watched the staff member who served me. She taped my typed address very securely to the post bag. I put my paw print on the requisite line...nothing dangerous in here  (unless you can strangle someone with a shawl knitted as a sample). 
I took the tracking number. 
    "It will be off later today," she assured me, "And should be there by Wednesday at the latest". Right. 
I prowled off. I was a happy cat.
I should have known better. 
I sent the tracking number to my friend P... and we  both thought she would have it ready for the stand on Thursday. 
It didn't get there. There was nothing on Thursday. There was nothing on Friday.
On Friday I tried to find out what had happened to the parcel. I had an automated response from Australia Post. I tried a social media site instead. Someone did respond from there. 
This morning, having given them more information, they sent another message. The parcel had been "slightly delayed" and would not be there until Monday.
Sorry, but that is far too late. A "slight delay" would be a day, at most two. Five days is not "slight". 
It is not slight because I had a parcel from a suburban post office in the same state yesterday. It had been posted on Thursday. I got it on Friday. It was not posted "Express" (which is supposed to guarantee next day delivery) but ordinary parcel post.
Now, if they can do it one way why can't they do it another?